Compressor control mechanism and method

ABSTRACT

The present invention is a mechanical refrigeration system and method of operation thereof including a compressor, a condenser, an expansion valve an evaporator, a hot gas bypass line and a hot gas valve. A control regulates the operation of the compressor and the hot gas valve and, upon determining that the compressor is to be shut off, first opens the hot gas valve for a predetermined time period to reduce any pressure differential between the high and low pressure sides of the compressor. This pressure reduction providing for reducing or eliminating any destructive compressor movement that would otherwise occur at shut down as the momentum of the moving parts of the compressor operate against a pressure differential. A similar method can be used to avoid such unwanted movement at start-up of the compressor.

[0001] The present application is a co-pending continuation-in-part ofU.S. patent application Ser. No. 09/639,868, filed Aug. 16, 2000, whichwas a co-pending continuation in part of U.S. Ser. No. 09/079,063, filedMay 15, 1998, which was a co-pending continuation-in-part of U.S. patentapplication Ser. No. 08/987,395, filed Dec. 9, 1997.

FIELD OF THE INVENTION

[0002] The present invention relates to refrigeration compressorcontrols and in general to such controls and methods designed to relievemechanical strain on the compressor.

BACKGROUND

[0003] Mechanical refrigeration systems are well known and are used in awide variety of products including, air conditioning and refrigerationequipment. It has long been understood that upon shut-off of acompressor, the compressing mechanism, such as the piston andcrankshaft, continue to rotate for a few revolutions due to the momentumthereof. However, there can exist a considerable pressure differentialbetween the high and low sides of the compressor that the piston mustwork against. This pressure difference can result in shaking of thecompressor as the piston comes to a stop there against. As a result, ithas long been known to have a spring mounting for the compressor so asto absorb this undesired movement in a way that safely dissipates thatenergy and eliminates mechanical damage to the compressor and itsassociated components. However, it has been found that in applicationswhere the compressor is required to endure frequent on/off cycles, aspring mounting may not suffice to protect the compressor assembly frommetal fatigue and subsequent failure.

[0004] An example of an application where frequent on/off refrigerationcycles are required is found in frozen carbonated beverage (FCB) makingand dispensing machines. FCB machines are well known in the art andgenerally utilize a freezing cylinder for producing a flavored slush icebeverage therein. An evaporator coil is wrapped around the exterior ofthe cylinder for cooling the contents thereof. The proper ratio of waterand a syrup flavoring is introduced into the cylinder and a scrapermechanism extends along the central axis of the cylinder and is rotatedto scrape thin iced or frozen layers of the beverage or food productfrom the internal surface of the cylinder. Mechanisms for maintainingthe slush at the desired consistency and include an electronic controlmechanism that sense the viscosity of the slush. Thus, the compressor isautomatically turned on to cool the cylinder and cause more freezing ofthe beverage if the viscosity is considered too low, and converselyshuts off the compressor once the viscosity has attained a predeterminedhigh level, thereby discontinuing the cylinder cooling. However, theslush is desirably held within a rather narrow viscosity range which initself requires frequent compressor on/off cycling. In addition, theamount of beverage dispensed overtime greatly influences this cycling asnew beverage must be introduced into the cylinder to make up for thevolume dispensed, and this newly introduced beverage must be cooled andturned into the desired slush state. Furthermore, increases in ambienttemperature can also shorten the time between the attainment of thedesired viscosity and the time the compressor must again be started dueto warming of the cylinder contents. Accordingly, it would be desirableto minimize any undesired compressor movement during the operationthereof.

SUMMARY OF THE INVENTION

[0005] The present invention serves to greatly reduce any unwantedcompressor movement. An application of the present invention can beunderstood in the context of a FCB machine wherein a freeze cylinderincludes an evaporator coiled around an exterior perimeter thereof. Thefreeze cylinder evaporator is connected on an inlet en to a pulsed typerefrigeration expansion valve and on its opposite or low pressure end toa compressor. As is well understood the compressor has a discharge tubeon its high pressure side connected to a condenser with the condenser,in turn, completing the refrigerant circuit and fluidly connected to theexpansion valve. A scraping mechanism within the cylinder provides forscraping frozen beverage from the inner surface of the cylinder. Acontrol mechanism provides for controlling the operation of therefrigeration system and hence the cooling of beverage within the freezecylinder. A defrost valve is positioned in a refrigerant line extendingbetween the discharge line and the expansion valve. As is understood,the control mechanism operates the defrost valve to open to flood theevaporator with hot refrigerant from the compressor high side.Typically, this is done in what is known as a defrost mode where theslush beverage is purposefully and periodically melted to removeunwanted large ice particles that have a tendency to form over time.

[0006] In operation, the control of the present invention includesprogramming that opens the hot gas defrost valve for a predeterminedshort period of time before the shut off of the compressor is requiredand holds it open for a predetermined period of time after shut off ofpower to the compressor is sensed. In this manner, those of skill canunderstand that such action serves to significantly reduce the pressuredifferential between the high a low sides of the compressor before andduring the shut off period. As a result thereof, any shaking of thecompressor at shut-off is greatly reduced by not having to come to astop against this high pressure difference. Conversely, and forbasically the same reason, those of skill will readily understand thatit is also possible to have the control herein open the hot gas valvejust prior to and/or extending to just after start up as a means to alsoequilibrate any unwanted pressure differential that may exist at thatpoint.

DESCRIPTION OF THE DRAWINGS

[0007] A better and further understanding of the structure, function andthe objects and advantages of the present invention can be had byreference to the following detailed description which refers to thefollowing figures, wherein:

[0008]FIG. 1 shows a perspective view of a frozen food productdispensing machine.

[0009]FIG. 2 shows an exploded view of a frozen food product cylinderassembly in conjunction with a first drive mechanism of the presentinvention.

[0010]FIG. 3 shows a plan view of the frozen food product cylinderassembly including the first drive mechanism of the present invention.

[0011]FIG. 4 shows a cross-sectional view along lines 4-4 of FIG. 3.

[0012]FIG. 5 shows a cross-sectional view along lines 5-5 of FIG. 2.

[0013]FIG. 6 shows an electrical schematic for the first drivemechanism.

[0014]FIG. 7 shows a cross-sectional view of a frozen food productcylinder assembly including a second drive mechanism of the presentinvention.

[0015]FIG. 8 shows a surface plan view of a magnetic drive disk of thepresent invention.

[0016]FIG. 9 shows a cross-sectional view along lines 9-9 of FIG. 7

[0017]FIG. 10 shows a perspective view of a frozen food productdispensing machine.

[0018]FIG. 11 shows an enlarged cross-sectional view of the driven disk.

[0019]FIG. 12 shows a perspective view of the present invention.

[0020]FIG. 13 shows a further perspective view of the present invention.

[0021]FIG. 14 shows a perspective view of the present invention havingthe panels removed therefrom.

[0022]FIG. 15 shows a partial cut away view of the water bath tank.

[0023]FIG. 16 shows a cross-sectional plan view of a carbonator/blendingbottle.

[0024]FIG. 17 shows a top plan view of the a carbonator/blending bottle.

[0025]FIG. 18 shows a schematic diagram of the refrigeration system.

[0026]FIG. 19 shows a schematic diagram of the fluid beverage system.

[0027]FIG. 20 shows a schematic diagram of the electronic control.

[0028]FIG. 21 shows a perspective view of the dual ice bank controlsensor.

[0029]FIG. 22 shows a end plan view along lines 21-21 of FIG. 20.

[0030]FIG. 23 shows a flow diagram of the viscosity monitoring controllogic.

[0031]FIG. 24 shows a flow diagram of the viscosity control logic

[0032]FIG. 25 shows a flow diagram of the ice bank forming controllogic.

[0033]FIG. 26 shows a flow diagram of the expansion valve control logic.

[0034]FIG. 27 shows a partial cross-sectional view of a furtherembodiment of a carbonator/blending bottle.

[0035]FIG. 28 shows a top plan view of the carbonator of FIG. 27.

[0036]FIG. 29 shows a perspective view of the internal baffle plate ofthe carbonator of FIG. 27.

[0037]FIG. 30 shows a perspective view of the combined level sensor andwater inlet of the carbonator of FIG. 27.

[0038]FIG. 31 shows a schematic of the compressor pressure equilibratingmechanism of the present invention.

[0039]FIG. 32 shows a flow diagram of the software control of thepressure equilibrating method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] A frozen food product making and dispensing machine is seen inFIG. 1, and generally referred to by the number 10. Machine 10 isillustrative of the type wherein the present invention can be applied.As seen by also referring to FIGS. 2-4, a stainless steel cylinder 12includes a cylindrical wall 14 and a stainless steel plate 16 welded toone end thereof forming a closed end surface and defining a cylinderinterior 18. A three phase stator 20 includes a ring portion 22 made ofmultiple lamination layers 22 a to which three electrical windings 23are wound and braided there around. Stator 20 is positioned on the endof cylinder 12 adjacent end wall 16 with cylinder wall 14 extendingthrough the center thereof.

[0041] A plastic spacer disk 24 is located within cylinder 12 and ispositioned against end wall 16. Disk 24 is made of a suitable food gradeplastic and includes a bearing 26 mounted centrally thereof. Asunderstood by also referring to FIG. 5, a rotor 30 includes a metal tubering section 32 having eight permanent magnets 34 secured equidistantlyaround a perimeter thereof wherein the North and South polaritiesthereof alternate. Ring 32 and magnets 34 are encased in a food gradeplastic 35, such as Delrin®, molded there around and leaving a centralshaft hole 36.

[0042] A scraper mechanism 40, also made of a suitable food gradeplastic, includes a central shaft 42 having a plurality of mixing rods44 and scraper blade supports 46 extending therefrom. A pair of scraperblades 48 are mounted on supports 46 wherein holes 50 thereof receivepin portions 52 of supports 46. Shaft end portion 54 extends throughhole 36 and is received in hole 28 of bearing 26. Shaft 42 also includesan attachment skirt 56 for securing thereof to rotor disk 30. Anopposite end 58 of shaft 42 is received in a short support section 60integral with extending from a plastic end cover 62. Cover 62 includesan O-ring 64 extending around a cylinder inserting portion 66 thereof.Cover 62 is secured to cylinder 12 by a plurality of bolts 67 a and nuts67 b. Flange 68, as with plate 16, is also made of stainless steel andwelded to cylinder 12. As is known in the art, cover 62 includes a hole70 for receiving a dispensing valve 72.

[0043] As is understood by those of skill, an evaporator coil 74 extendsaround the exterior of cylinder 12 and includes an inlet fitting 74 aand an outlet fitting 74 b. Fittings 74 a and 74 b are connected to highpressure line 76 and low pressure line 78 respectively of a mechanicalrefrigeration system including a compressor 80 and a condenser 82.Insulation 84 extends around cylinder 12 and evaporator 74. A beverageinlet line 86 is connected to a cylinder inlet fitting 88 and a beveragereservoir or mixing tank 90. A pair of cylinders 12 can be securedwithin the housing of dispenser 10 and supported therein by a framework92 thereof.

[0044] As seen in the schematic of FIG. 6, a power supply 94 includes aninverter 96 for converting 220 VAC to a three phase DC current. Thisthree phase current is connected to the three winding 23 of stator 20.Thus, those of skill will understand that stator 20 and rotor 30comprise a DC motor. In operation, therefore, the three phase currentinduces movement of rotor 30 which, in turn, rotates scraper mechanismor assembly 40. Thus, with a beverage, for example, delivered withincylinder 12 through line 86 and cooling thereof by evaporator 74 and itsassociated refrigeration system, frozen beverage can be produced byscraping thereof from the interior surface of cylinder 12. The use of arotor around which a food grade plastic has been molded permits thatpart of the DC drive motor to be internal of the cylinder and in contactwith the food product. In general, all the components of the presentinvention are made of or coated with a suitable food grade material.Thus, the present invention comprises a drive mechanism for a frozenfood product machine utilizing an internally scraped cylinder whereinthe drive motor therefore is an integral part of the cylinder assembly.As a result, no dynamic seal or external shaft bearing is needed for thescraper mechanism. Thus, the traditional external motor, dynamic seal,external shaft bearing and transmission can be eliminated.

[0045] In one example of the integral DC motor drive embodiment of thepresent invention, the drive motor is used in a cylinder that isapproximately 15 inches long with a diameter of approximately 4.5inches. The drive motor in such an application is designed to produce atorque of approximately 110 inch/lbs. at 100 RPM's.

[0046] In a second embodiment of the present invention, as seen in FIGS.7-9, a cylinder 100 has a cylinder wall 102 and an end plate 104defining a cylinder end surface 106. An AC motor 108 is secured to atransmission 110 which is in turn secured to a plastic collar 112attached to plate 104. Transmission 110 includes a drive shaft 114 towhich is attached a magnetic drive disk 116. As seen in FIG. 8, disk 116includes six permanent magnets 118 secured thereto around a perimeter ofone side or face thereof wherein the North and South polarities thereofalternate. Magnets 118 are positioned to face and be held closelyadjacent end surface 106.

[0047] Within cylinder 100 a food grade plastic spacer 120 is positionedagainst the interior surface of end wall 106. Spacer 120 includes acentral bearing 122 and includes an annular wall portion 124 defining adisk retaining space 126. A food grade plastic collar 128 is received instainless steel bearing 122 and on one end thereof has a driven magneticdisk 130 secured thereto. As seen by also referring to FIG. , astainless steel disk 130 includes a plurality of permanent magnets 131arranged on a metal ring 132. Ring 132 is secured to disk 130 within anannular groove 134 thereof as defined by walls 135. A plastic collar orring cover ring 136 is secured to walls 135 around a top perimeterthereof for sealably enclosing magnets 131 and ring 132 within annulargroove 134. Magnets 131 of disk 130 are positioned to face and lieclosely adjacent the interior surface of end wall 106.

[0048] As with the first drive embodiment described above, the seconddrive embodiment also includes a scraper mechanism 40 having a centralshaft 42 having a plurality of mixing rods 44 and scraper blade supports46 extending therefrom. A pair of scraper blades 48 are mounted onsupports 46 wherein holes 50 thereof receive pin portions 52 of supports46. A shaft end portion 140 is shaped as seen in FIG. 9, to provide fordriving receiving thereof in a similarly shaped bore 142 of collar 128.As with the previously described embodiment, an opposite end 144 ofshaft 42 is received in support 60 extending from plastic end cover 62.Flange 68, as with plate 104, is also made of stainless steel and weldedto cylinder 100.

[0049] As with the previously described DC motor embodiment, cylinder100 includes an evaporator coil 74 extending there around that includesan inlet fitting 74 a, an outlet fitting 74 b and a foodproduct/beverage inlet 88 for connection as stated above. Insulation 84also extends around cylinder 100 and evaporator 74. A pair of cylinders100 can be secured within the housing of dispenser 10 and supportedtherein by a framework 92 thereof.

[0050] In operation, motor 108 operates through transmission 110 torotate magnetic disk 116. Due to the magnetic coupling between disk 116and 130 as they face each other on opposite sides of end wall 106,rotation of disk 116 results in the rotation of disk 130, and hence,rotation of scraper mechanism or assembly 40. Thus, with beverage orfood product delivered within cylinder 100 through line 86 and coolingthereof by evaporator 74 and its associated refrigeration system, frozenbeverage can be produced by scraping thereof from the interior surfaceof cylinder 100. This magnetic drive embodiment, as with the DC motorembodiment herein, eliminates the need for a dynamic seal and anexternal bearing with respect to the shaft 42 of the scraper mechanism40. Also, plate having an annular groove for receiving the magnets andring wherein those components are sealed therein by a food grade plasticring, permit the driven disk 130 to be in contact with food product,i.e. permits a magnetic drive approach or mechanism that is foodcompatible.

[0051] A further embodiment of the present invention is seen in FIGS. 12and 13 and generally referred to by the numeral 200. Machine 200 has anouter housing having removable panels, including side panels 201, a toppanel 202 and a display door 203 having a transparency window 204.Panels 201 and 202 include louvers 205 and an air flow grate 206,respectively. A plurality of light fixtures 208 are secured door 203,and are used for back lighting a transparency 210. Door 203 is hinged toa front surface of machine 200, and as seen in FIG. 13, can be swung toan open position for facilitating access to fixtures 208 and to userinterface 212.

[0052] As seen by also referring to FIG. 14, machine 200 includes aframework 213 for supporting various internal components as well as thevarious portions of the exterior housing including housing panels 201and 202, and access door 203. A pair of freeze cylinder assemblies 214are held within separate insulated housings 216. Both cylinderassemblies 214 are of the type disclosed above in FIGS. 2-6 herein andhave DC drive motors 217 as also shown and described therein. However,unlike dispenser 10, embodiment 200 includes a water bath tank 218. Tank218 includes sides 219 for retaining a volume of water therein. As seenby also referring to FIG. 15, tank 218 includes an ice bank formingevaporator 220. Evaporator 220 is held therein by support means 222 andpositioned thereby adjacent three of the four interior surfaces of sides219.

[0053] A pair of specialized carbonator/blender bottles 224 are retainedin tank 218. Bottles 224 are seen in greater detail in FIGS. 16 and 17and are essentially the same as the carbonator disclosed in co-pendingU.S. patent application Ser. 08/761,191, filed Dec. 5, 1996, whichapplication is incorporated herein by reference thereto. Bottles 224each include a cylindrical stainless steel body 226 having a bottom end228 and a top open end 230. A plastic disk 232 is sized to fit withinopen end 230 and sealed there against by an O-ring 234. Disk 232 isreleasably retained in open end 230 by means of a wire spring or clip238. Clip 238 can be grasped by ends 238 a thereof to remove from orinsert into slots 240, cut through cylinder 226, through which radiusedcomers 238 b are inserted. Disk top surface 242 is designed to cooperatewith clip 238 to minimize any accidental disengagement thereof with disk232. In addition, disk 232 includes a fluid inlet 244, a gas inlet 246for receiving pressurized carbon dioxide gas and a fluid outlet 248.Disk 232 also includes a safety release pressure valve 250 and a liquidlevel sensor 252. Sensor 252 includes a rod 254 that is positionedwithin bottle 224 having a movable float 256 free to slide there along.Rod 254 includes one or more magnetically actuated switches 258 thereinand along the length thereof, and float 256 includes a magnet 260. As isunderstood in the art sensor 252 operates whereby float 256 is carriedby the level of liquid within 224. As magnet 258 moves adjacent one ofthe switches 258 turning it on, then a level can be indicated. Inlet 244is fluidly connected to a J-tube 262, and outlet 248 is fluidlyconnected to a tube 264 extending to a point adjacent bottle end 228.

[0054] Water bath tank 218 also includes a two serpentine coils of heatexchange stainless steel tubing 262 positioned together and adjacent afourth or remaining interior surface side against which evaporator 220is not positioned. An agitator motor 264 is secured to a top cover panel266 and includes a shaft and attached agitator blade, not shown, foragitating the water within bath 218.

[0055] As understood by also referring to FIG. 18, the refrigerationsystem used in machine 200 includes a refrigeration compressor 270connected by refrigerant high pressure and low pressure lines 271 a and271 b, respectively, to a condenser 272. As is well understood in theart, line 271 b includes a discharge line portion 271 b′ that emanatesdirectly from compressor 270. Each cylinder assembly 214 includes anevaporator coil 274 and each evaporator coil has associated there withan electronically pulsed expansion valve 276 and a hot gas defrost valve278. Hot gas valves 278 are fluidly connected to a refrigerant bypassline 278 a and expansion valves 276 are provided refrigerant fromcondenser 272 along line 276 a. Also, each coil 274 includes an inlettemperature sensor 277 a and an outlet temperature sensor 277 b. The icebank forming evaporator 220 is also connected to compressor 270 by highand low pressure lines 271 a and 271 b. Evaporator 220 also hasrefrigerant metered therein by an electronically pulsed expansion valve280. Evaporator 220 also includes an inlet temperature sensor 282 and anoutlet temperature sensor 284.

[0056] An ice bank 286 forms on evaporator 220 and, as furtherunderstood by referring to FIGS. 21 and 22, the size thereof isregulated by a pair of ice bank sensors 288 a and 288 b. Sensors 288 aand 288 b each include a housing 290 wherein a pair of wire probes 291extend. Probes 291 are connected to wires 292 that provide connection tothe control of the present invention, further described below. Eachhousing 290 is secured to an attachment plate 293. Sensor 288 a issecured to a first level surface 293 a of plate 293 and sensor 288 b issecured to a second outer level surface 293 b thereof. Thus, adifferential distance D, as indicated by the dashed lines of FIG. 21, iscreated between the probes 291 of each of the sensors 288 a and 288 b. Aflange 294 and hook 295 provide for attachment of plate 293 to asuitable support means within ice bath 218 at a suitable distance fromevaporator 220.

[0057] A schematic of the beverage fluid delivering system used in thepresent invention can be understood by referring to FIG. 19. A seentherein, an inlet water line 300 is connected to a source of potablewater for delivering the water, first to a T-fitting 302 and then to abrixing or ratioing valve 304. A second line 306 extends from fitting302 to a float operated valve 308 positioned within water bath tank 218.A third line 310 is connected to a source of beverage syrup, such as abag-in-box 312. Line 310 includes a fluid flow sensor 314 and is fluidlyconnected to a further brixing valve 316. Sensor 314 is of the pistonfluid contact type as, for example, model FS-3, as manufactured by GemsSensors, of Plainville, Conn. Valves 304 and 316 provide for mixing thewater and syrup at a ratio of typically 5 to 1 respectively. The fluidcomponents flow to a Y-fitting 318 and are mixed together. A pump 320pumps the properly ratioed, but as yet noncarbonated beverage, to a testvalve 322 and from there to one of the heat exchange serpentine coilslocated in tank 218. Valve 322 normally directs the beverage to a coil262, but can be manually operated to divert and deliver a test sample ofthe beverage along line 324 to an outlet point. In this manner thebeverage can be easily tested to check for the proper ratioing thereofby valves 304 and 316. The beverage flows from a coil 262 to inlet 244of the associated blender/carbonator bottle 224. A pressurized source ofcarbon dioxide gas 326 provides carbon dioxide first to a valve 328.Valve 328 provides for diverting carbon dioxide gas to bag-in-box 312 inthe example where a carbon dioxide pump 327 is used to move syruptherefrom. Those of skill will realize that other means, such aselectric pumps can be used to pump the syrup whereby valve 328 would notbe required. Or, carbon dioxide gas can be used to propel the syrup froma rigid stainless syrup tank. Regulator valves 330 a and 330 b providethe carbon dioxide at a desired pressure to the gas inlets 246 of eachblender/carbonator 224 positioned in tank 218. It will be appreciatedthat FIG. 18 shows a schematic of one of the beverage fluid systems,there being one for each cylinder assembly 214. Thus, in a machine 200having two cylinders 214, there are two brixing valves 304, two brixingvalves 316, two coils 262, tow pumps 320, two flow sensors 314, and twocarbonator/blenders 224. The outlets of each blender/carbonator 224 areconnected to outlet lines 332 that are connected first to manual valves234 and then to inlets 236 of each of the cylinders 214. Valves 234provide for manually stopping the flow of carbonated beverage tocylinders 214, primarily for the purpose of facilitating servicingthereof.

[0058] Sensors 314 provide a major advantage in that they are able tosense when the syrup has sun out whether the syrup is delivered from abag-in-box or from a stainless tank. Prior art machines required thatthere be two sensor systems, one for either syrup containing source. Apressure sensor was required for the bag-in-box as, when the bag becameempty, there would be no pressure, and that would indicate a sold outcondition. However, if a tank was used the carbon dioxide gas used topropel the syrup would indicate to the pressure sensor that syrup waspresent, when in fact, it was not. Thus, a tank syrup reservoir requireda float sensor that would only be affected by actual liquid syrup.Therefore, sensor 314 eliminates having redundant systems and theassociated cost and complexity thereof.

[0059] It can be appreciated that the present invention provides for thecooling of a volume of beverage within coils 262 prior to introductionthereof into each blender/carbonator 224. Thus, the beverage will havereached a temperature of approximately 36 degrees Fahrenheit prior tothe introduction thereof into a corresponding container 224. Inaddition, each blender/carbonator is also held at the same temperaturebeing immersed in the cold water bath. Therefore, the carbonation of thebeverage that occurs therein can reach a desired level of saturation atmuch lower carbon dioxide gas pressures than if the mixing wereoccurring in a bottle held at a much warmer room ambient temperature. Inaddition, the present invention has a much greater beverage productioncapacity, as an ice bank presents a large cooling reserve that wouldotherwise not be available unless an exceedingly large refrigerationsystem is used. Thus, as the beverage is presented to the freezecylinder at a very low temperature, the cooling required of the freezecylinder evaporators is much lower so that overall, the presentinvention works much more efficiently than do comparable prior artmachines that produce semi-frozen beverages or food products frombeverage delivered to the cylinders at ambient temperatures.

[0060] As seen in FIG. 20, the present invention uses a distributedelectronic control having a product delivery control board 340 for thecontrol of each cylinder 214. A main logic board 342 is connected toeach control board 340, and there is one inverter board 344 for each ofthe two cylinders 214. The boards communicate as is generally indicatedby the arrows of FIG. 19. Main board 342 receives inputs from the userinterface 212, and from each of the product delivery board (340) on thesystem, as well from the CO₂ pressure sensor, an H₂O pressure sensor,high/low line voltage, ice bank thickness (min), ice bank thickness(max.), ice bank evaporator input temperature and ice bank evaporatoroutput temperature. Main board 342 controls the operation of compressor27- on/off, ice bank agitator motor and ice bank pulse valve. Eachproduct delivery board receives inputs from its associated syrup flowsensor 314, level sensor 252, evaporator input temperature sensor,evaporator output temperture sensor, product viscosity sensor and beatermotor error, and controls the operation of its associated beater motoron/off, defrost valve on/off, pulse valve on/off, syrup valve on/off,H₂O valve on/off, disp. Valve lockout, product status light andblendonator pump 320. The inverter board 344 provides for inverting the240 VAC supplied current to the 340 VDC current used by motors 217. Inaddition, it senses the current draw being placed on each motor 217 andruns them at a constant 120 revolutions per minute (RPM).

[0061] A distributed control is used to better accommodate machineshaving more than two cylinders 214. Thus, the main board 342 can bedesigned to work with more than two product delivery boards. In thismanner, a cost saving can be had as opposed to having a main controlboard having to be designed specifically for each machine having aparticular number of cylinders. The main board receives the commandsfrom the operator interface, and distributes this information to theappropriate board. For instance, if the operator wants to turn oncylinder #1, the main board will send the “on” command to the productdelivery board on cylinder #1. The PDB will then tell the inverter boardto apply power to stator #1, as well as request the compressor to comeon and begin pulsing the pulse valve for cylinder #1.

[0062] A better understanding of the control logic utilized by thecontrol of the present invention to monitor the viscosity of thebeverage, control the viscosity of the beverage and to regulate the icebank can be had by referring to the flow diagrams thereof shown in FIGS.23-26. Viscosity is monitored as a function of the current draw of theDC drive motor for the particular cylinder. In addition, each motor 217,as stated above, is controlled to operate at a constant 120 RPM rate.Thus, the more viscous the beverage the greater load and current draw onthe motor 217 to maintain the set point rotational speed. Since themotors 217 are directly driving the cylinder scraper mechanisms, and theRPM's are kept constant, there exists a very direct correlation betweenthe current draw of the motors and the viscosity of the food product.Each product delivery board has look up tables that correlate thecurrent draw to an arbitrary viscosity number scale, which scale isutilized by each board to indicate a level of viscosity of the beveragewithin the cylinder. As seen in FIG. 23, a start point is indicated byblock 350. The viscosity is monitored by each board 340, wherein atblock 351 it is determined if the viscosity is below a preset viscosityminimum. If the viscosity is below that minimum, and it has been belowthat minimum for greater than one second, block 352, then at block 354,it is determined if compressor 270 is on. If compressor 270 is on, thenthe viscosity is controlled at block 356. A more detailed description ofthe viscosity control is contained below with reference to FIG. 24. Ifcompressor 270 is not on, then the control inquires if it has been offfor more than two minutes, block 358. If it has, then compressor 270 isturned on at block 360 and viscosity is controlled at block 356. Atblock 361, it is determined if the desired viscosity has attained apredetermined desired level. If it has, the compressor is turned off atblock 362 and the control goes to return at block 364 and monitors theviscosity. If at blocks 351, 352 or 358 it is determined, respectively,that the viscosity is not below viscosity minimum or the viscosityminimum was not maintained for more than one second or that thecompressor has been off for less than two minutes, then the control, atblock 366, determines if the float sensor 252 of the associated bottle224 has been activated to signal for more beverage to be pumped therein,i.e. has beverage been drawn from the associated cylinder wherebyfurther beverage must be replaced therein, and in its associatedcarbonator/blender 224. If the float has been activated, then furtherbeverage is added to the cylinder by control of pump 320 and operationof valves 304 and 316. The control then inquires, at block 368, if thecompressor is on, and turns the compressor on as needed or proceeddirectly to viscosity control, block 356. If the sensor 252 has not beenactivated to deliver more beverage within its associated bottle 224,block 366, then the control determines if 5 minutes has elapsed sincethe last refrigeration cycle, block 370. If less than the 5 minutes haselapsed, the control goes to return, block 372 where viscosity ismonitored. If more than 5 minutes have elapsed since the last operationof the compressor, the control then inquires, at block 368, if thecompressor is on, and turns the compressor on as needed, block 360, orproceeds directly to viscosity control, block 356. The viscosity controlof the present invention can be better understood in terms of the flowdiagram of FIG. 24. At the start block 380 the control moves to blocks381 and 382, where the board determines the inlet and outlettemperatures, respectively, of the particular evaporator coil 274, andat block 384, measures the barrel viscosity. At block 386 it isdetermined if the viscosity is greater than a pre-selected viscositymaximum. If it is, the control queries if the particular coil 274 is inthe “top off mode”, block 388. If not, the top off mode is begun atblock 390. The top off mode is a sequence that permits a relativelyaccurate determination of the beverage viscosity. Thus, at block 392 a 3second timer is started during which the associated pulse valve 276 isclosed, block 393. Further refrigeration is stopped for this timeperiod, however the scraper mechanism continues to turn. At block 394pulse valve 280 is operated to provide for building of the ice bank. Afurther understanding of the control of the ice bank will be had belowin reference to FIG. 25. At block 396, the maximum viscosity sensedduring the top off period is recorded. If the 3 second timer has timedout, block 398, then the control determines if the difference betweenthe present viscosity and the maximum viscosity currently sensed duringtop off is lesser or greater than a pre-selected viscosity delta ordifference, block 400. The delta is contained in a look-up table and isan experimentally derived number. If the delta is not exceeded, thismeans that the viscosity of the beverage is at the desired level andrefrigeration of the cylinder can be stopped, block 402, and the controlcan go to return 404. If the measured delta is too large, i.e. in excessof the preset delta, this indicates that the beverage is not viscousenough. Then the control goes to block 406 ending top off and continuingrefrigeration and goes to return 404. Ice can not be built on evaporator220 during refrigeration of either coil 274. Only when both cylindersare satisfied and/or are otherwise not being cooled. Thus, if the othercylinder evaporator 274 is being cooled, cooling of evaporator 220 isnot permitted. Therefore, ice can be formed during top off if the othercoil 274 is not being cooled or if both are in top off. As a consequencethereof, if top off has ended as the delta was too large, block 400,further cylinder cooling is required and cooling of evaporator 220 isstopped, if one or both cylinders 214 are in a refrigeration sequence.At block 386, if the viscosity is below the preset viscosity maximum,then at block 408 the temperature of the particular inlet of theassociated coil 274, as measured by sensor 277 a, is determined. If thattemperture is greater than 40 degrees Fahrenheit, then aproportional/integral/differential “PID” calculation is made to controlthe temperature down to 40° F., block 410. As is understood in thecontrol art, PID control generally follows the equationPID=E_(c)(Kp)+(E_(p1), E_(p2) . . . E_(c))K_(i)+((d)E/(d)t)K_(d). whereEc is the current error, K_(p) is a proportional proportionalityconstant, E_(p1) . . . represent previous error values, K_(i) is theintegral proportionality constant, (d)E/(d)t is the rate of change ofthe error and K_(d) is the associated differential proportionalityconstant. The value (E_(p1), E_(p2) . . . E_(c)) represents an equation,such as the averaging of the E values, that, multiplied by K_(i)represents the portion of the PID valve that is based on the size theerror over time. The E_(c)(K_(p)) value represents the portion of thePID valve that is based on the size of the currently measured error. Allthree variables can be used produce a very accurate understanding of howa particular target point is being approached. In the present invention,PID control is used to control to a 40 degree F. set point with a highdegree of accuracy. The particular pulse valve 276 is operatedaccordingly, block 412, as per the PID output. If at block 408 thetemperature of the inlet is less than 40 degrees F., then it isdetermined if the outlet temperature, as determined by sensor 277 b, isgreater than 46 degrees F., block 414. If that temperature is greaterthan 46 degree F., then the logic control returns to blocks 410 and 412and controls the temperature of the inlet to 40 degrees F. Thus, thecontrol is first seeking to establish a delta T of six degrees betweenthe coil 274 inlet and outlet temperatures at a particular startingpoint where the inlet temperature is 40 degree F. and an outlettemperature is 46 degrees. When that is accomplished, then, at block416, the PID control can be used to simply control the delta T to 6degrees F. whereby the inlet and outlet temperatures can fall below 40and 46 respectively, as long as the delta T of 6 degrees between them isaccurately maintained.

[0063] A better understanding of the ice bank control herein can be haswith reference to FIG. 25. At the start point 420, the control thenstarts a 30 second ice measure timer, block 421. During that 30 secondinterval ice sensors 288 b and 288 a are measured, respectively, blocks422 and 423. After the 30 second timer has timed out, block 424, thecontrol determines if either cylinder 214 is calling for refrigeration,block 425. If either cylinder is calling for refrigeration then it isdetermined if the compressor 270 is running, block 426. The compressoris then turned on, block 427, or the control goes directly to block 428.At block 428 it is determined if either cylinder is in a normal operatemode, i.e. not in top off and requiring refrigeration. If eithercylinder is in a normal operating mode, then no refrigeration of the icebank can occur and the control goes to return, block 429. If one or bothare not in normal mode, i.e. in top off mode, then the particular pulsevalve 276 is pulsed at the top off rate, block 430 and the control goesto return 431 the rate that is determined to maintain a 20 degree F.temp. If, at block 425, neither cylinder 214 is calling forrefrigeration, then ice bank sensor 288 b is polled to determine if iceis present, block 432. If sensor 288 b senses ice, then no more buildingof ice is desirable so, if the compressor is running, block 434, it isturned off, block 435 and valve 280 is opened for 5 seconds to equalizepressure, block 436, and the control goes to return, 438. If sensor 288b does not sense ice, then at block 440, the control looks at sensor 288a to see if it senses ice. If sensor 288 a so indicates, then thecontrol follows blocks 434, 435, 436 and 438. If sensor 288 a does notsense ice, then ice can and should be added to the ice bank, it havingeroded to a point that a greater cooling reserve is desirable. Thus, atblock 444, if the compressor is running, pulse valve 280 is operated tocool evaporator 220 and build ice thereon, block 445. If the compressoris not running, it is turned on, block 446. Pulse valve 280 is operatedas per the flow diagram valve control loop delineated in FIG. 26 below.

[0064] As can be understood by referring to FIG. 26, at a start point450, the control measures evaporator 220 inlet temperature using sensor282 a, block 452 and then measures the outlet temperature thereof usingoutlet sensor 282 b, block 454. The delta T of evaporator 220 iscontrolled in substantially the same manner as previously described forthe cylinders 214. Thus, the inlet temperature is first sensed, block456, and moved down using a PID control, block 458, and a valve pulsetimer as per that PID calculation, block 460, to a preset temperature of20 degrees F. Once that value is attained, the control goes to return,block 462. If the inlet temperature is less than 20, then the controldetermines if the outlet temperature is greater than 40 degrees, block464. If it is then the control returns to blocks 458 and 460 to move theinlet temperature to 20 degrees F. Once the inlet temperature is equalto 20 degrees F. and the outlet temperature is equal to −40 degrees F.,then at block 464, the control then moves to block 466. At block 466 aPID control is utilized to maintain a delta T of 20 degrees F. The pulsevalve 280 is set accordingly, block 468, and the control goes to return,block 270.

[0065] Those of skill will understand that the present inventionprovides for the production of a semi-frozen food product in a mannerthat maximizes the efficiency of operation of the refrigeration systemthereof. The life of the compressor is extended as refrigerant gas canbe alternately directed to either of the cylinder evaporators 274 or theice bank evaporator 220. In particular, the two ice bank sensors providefor an incremental area between an ice bank maximum size and an ice bankminimum size where the ice bank can be grown to prevent the compressorfrom running and building pressure after both the valves 276 are closed.In this manner the compressor is not short cycled or presented withdamaging high pressures when an expansion valve is closed. Since theerosion of the ice bank generally occurs at a faster rate than it isbuilt up, it is contemplated that there will be very few or no occasionswhere the refrigerant can not be diverted to evaporator 220 so as toprotect the compressor.

[0066] Furthermore, as an ice bank is used, a large cooling reserve canbe built up during the times that neither cylinder 214 is calling forrefrigeration, such as when the beverage therein is of sufficientviscosity, or where the cylinders have been shut down entirely during a“sleep mode”, well known in the art, where no drinks will be dispensed.Also, as the PID control permits a much smaller delta T to be maintainedin a safe manner, better efficiency of cooling is obtained fromevaporators 274 and evaporator 220. Dispenser 200 therefore has asubstantial advantage over comparable prior art machines in terms ofrefrigeration system design parameters. Dispenser 200 can use a muchsmaller compressor to do the work of a larger compressor in a prior artmachine, or obtain more cooling from the same sized system.

[0067] As seen by again referring to FIG. 3, framework 213 defines threeareas 500, 502 and 504. Top area 500 will be understood to retain waterbath 218, condenser 272 and compressor 270. Middle area 502 retainscylinder packs 216, and the expansion valves 276 and 280 and the defrostvalves 278. Lower section 504 includes beverage pumps 320 and ratiovalves 304 and 316. As is known in the art, defrost valves 278 serve toprovide hot gas defrost of each cylinder 214. Such defrost isperiodically required to remove large particles of ice that canperiodically form within a cylinder. A filter grate, not shown, issecured to condenser 272 on the exterior side of beverage machine 200opposite from the fan 273 thereof.

[0068] As seen by referring to FIGS. 27 and 28, a further improved andpreferred embodiment of a carbonator of the present invention is seenand generally indicated by the numeral 600. Carbonator 600 is of thesame general design as previously described carbonator 224 and includesa cylinder 602 having an bottom end 604, a perimeter side wall 606 and atop open end defined by a perimeter edge 608. As with carbonator 224, aplastic disk or plug 610 is retained in the top end of cylinder 602 by aspring wire 612 and sealed therein by an O-ring 613 extending around aperimeter thereof. Further, as with carbonator 224, a retaining wire 612is bent into a rectangular configuration that is retained in grooves 614of disk 610, and includes four comer portions 612 a for insertionthrough holes 616 extending through side wall 606 adjacent edge 608.Also, as previously described with respect to carbonator 224, wire 612includes two vertical ends 612 b for effecting release of disk 610 fromcarbonator 600.

[0069] Disk 224 includes an outlet tube 620 having an upper end 620 aand a lower end 620 b, and a carbon dioxide gas inlet tube 622 having anupper end 622 a and a lower end 622 b. A plastic tube 624 is fluidlyconnected to end 620 b of tube 620 and extends within cylinder 602 andterminates therein adjacent bottom end 604. A further plastic tubesection 626 is fluidly connected on its proximal end to bottom end 622 bof inlet 622 and on its distal end to an adapter fitting 628. Adapterfitting 628 permits fluid tight securing of tube 626 to plastic diffuser630. Diffuser 630 has a larger diameter than tube 626 and has aperimeter side wall 630 a and a bottom end 630 b defining a closedinterior space 632. Diffuser 630 is preferably made of a porous plasticmaterial such as a microporous polyethylene as manufactured by PorexCorporation of Fairburn, Ga.

[0070] As understood by also referring to FIG. 29, carbonator 600includes a metal baffle plate 634. Plate 634 is round and sized to fitwithin cylinder 602. Plate 634 includes a plurality of primary flowholes 636, a larger hole 638 for receiving tube 624 there through, and asecondary flow hole 640. Plate 634 is supported at a level withincylinder 602 above end 604 approximately one quarter of the distancebetween bottom end 604 and disk 610. Plate 634 is so supported by a pairof U-shaped legs 642 secured thereto and that rest on bottom end 604.

[0071] Carbonator 600 includes a combined level sensor and beveragemixture inlet 644 as seen by also referring to FIG. 30. Sensor 644includes a singularly molded plastic body having a top end portion 644 aand a bottom end portion 644 b. Top end 644 a includes threads 646 forproviding threaded screw securing thereof to disk 610 in a correspondingthreaded hole 646 therein. A mixture inlet tube 648 is integral with endportion 644 a and includes a top end 648 a and a bottom end 648 b. Levelsensor bottom portion 644 b includes shaft portion 652 terminating in aflow disk 654. A further shaft 656 is secured to a proximal end of shaftportion 652 and includes a buoyant float 658 slideably secured thereto.As is understood, float 658 includes a magnet 660 for interacting with aswitch 662 within shaft 652. Wires 664 provide for connection of switch662 with a control mechanism, not shown.

[0072] In operation, an outlet line, such as line 232 seen in FIG. 19,is connected to end 620 a of tube 620 and provides for delivery ofcarbonated beverage to a cylinder, such as cylinder 214 of FIG. 14. Asource of pressurized carbon dioxide gas, such as 326 shown in FIG. 19,is connected to end 622 a of inlet 622. and a mixture line, as alsodepicted in FIG. 19 and indicated by the numeral 262, is secured to end648 a of inlet tube 648. As is understood a pump, such as pump 320 ofFIG. 19, is operated by a electronic control as a function of the levelof the beverage mixture within cylinder 602. Such level is determined bythe level of float 658 as it is carried up and down shaft 656 by thelevel of the fluid beverage mixture. Thus, pump 320 is turned on whenfloat 658 drops to a level wherein magnet 660 is no longer sufficientlyclose to switch 662 to maintain it in a closed non conducting position,which signals the need to replenish cylinder 602 with beverage mixture.Such minimum level is indicated by the horizontal line in FIG. 27 asmarked by the letter M.

[0073] Specifically, it can be understood that the beverage mixture isdelivered to tube 648 and exits end 648 b thereof. As end 648 b ispositioned centrally of and above deflection disk 654, the mixtureimpacts disk 654 and is deflected thereby, as indicated by the arrows ofFIG. 27, in various directions transverse to the initial downward flow.It can be appreciated that disk 654 protects float 658 from anydisruption thereof and any false level readings that a direct flowimpact thereon may cause. Thus, disk 654 permits a combination of themixture inlet and level sensing elements thereby permitting cost savingsin terms of parts reduction and assembly time.

[0074] It can be understood that the level of beverage mixture incylinder 602 is determined by level sensor 644 to always be maintainedwell above the level of plate 634. Generally, the beverage mixture tendsto exist as a gradient of less carbonated to more carbonated in adirection from a top possible level thereof to the fraction thereofresiding closely adjacent bottom end 604. Thus, outlet tube 624 tends todesirably extract the most carbonated mixture from the cylinder due toits distal end position closely adjacent cylinder end 604. However, itis believed that such gradient is easily disrupted by the inflow ofbeverage mixture and/or carbon dioxide gas resulting in someinadequately carbonated beverage product being dispensed to cylinder214. Also, where a carbon dioxide gas inlet tube, such as tube 262 ofFIG. 16, terminates within a carbonator cylinder, the efficiency ofmixture of the gas with the beverage component is not optimized. Thus,diffuser 630 serves to introduce the gas into the beverage as veryfinely divided bubbles providing for a much increased surface area ofmixture there between. In this manner it is thought that the carbondioxide gas is more rapidly put into solution in the beverage.

[0075] It was also found that plate 634 serves to partially separate thebeverage mixture into two regions, one above the plate and one below.This separation appears to provide for both a preferential carbonatingof the beverage in the upper region as the diffuser 630 is locatedtherein, and provides for a preferential dispensing of the lowerportion. It is though that plate 634 prevents disruption of theaforementioned carbonation gradient permitting more orderly andefficient carbonation of the beverage, which enhances the overall rateand efficiency of carbonation. In addition, the use of the diffuser 530,as mentioned above, further contributes to carbonation speed andefficiency. Thus, carbonator 600 provides for the ability to fullycarbonate a large volume of beverage mixture rapidly under high drawand/or high ambient temperature conditions. The primary holes 636 permitbeverage flow there through under conditions of low or normal dispensedemand in a direction from the upper region t the lower region. Thelarge flow hole 638 insures against starving of outlet tube 620 underconditions of high dispense demand.

[0076] As seen by referring to FIG. 31, a simplified schematic of arefrigeration system generally designated 700 is shown. A compressor 701is fluidly connected by a high pressure side refrigerant line 702 to acondenser 704. Condenser 704 is cooled by a fan 705 and is fluidlyconnected by a refrigerant line 706 to an expansion valve 708. Valve 708serves to meter compressed and cooled refrigerant into an evaporator 710as determined by a microprocessor based electronic control 712. Control712 also controls the on/off operation of compressor 701 and theoperation of fan 703. Evaporator 710 is fluidly connected to compressor701 at a low pressure side 714 thereof. A hot gas defrost valve 716 isfluidly connected to a bypass line 718 that extends between refrigerantline 702 and evaporator 710. Control 712 also controls the on/offoperation of valve 716.

[0077] The method of control of the foregoing refrigeration system 700is seen by referring to the flow diagram of FIG. 32. At a start-up block720 it will be assumed that compressor 701 is running to provide coolingof evaporator 710 in the conventional manner well known in the art. Atblock 722 control 712 determines if the cooling of evaporator 710 shouldstop. If the answer is no, compressor 701 is allowed to continue to run,if the answer is yes, compressor 701 is to be shut off. The shut offprocedure is commenced at block 724 where expansion valve 708 is firstclosed and hot gas valve 716 is subsequently opened for a predeterminedperiod of time. At block 726 it is determined if that predeterminedperiod of time has timed out. Once the answer at block 726 is yes,control 712 shuts off the current to compressor 701 at block 728. Oncethe current to compressor 701 is shut off, a second predetermined periodof time is counted at block 730. When that second time period haselapsed, i.e. “yes” at block 730, hot gas valve 716 is closed at block732 and the system returns to the run mode at block 720.

[0078] It will be appreciated by those of skill that the first andsecond time periods surrounding the shut-off of electrical power tocompressor 701 permit the refrigerant pressure differential atcompressor 701 as between the high and low pressures sides, to movetowards a state of equilibration. As a result of this pressure leveling,the rotating internal components of compressor 701, not shown, can cometo a smooth stop that eliminates or greatly reduces any destructiveshaking of compressor 701. It has been found that the high pressure line702, and in particular the discharge portion thereof that line thatdirectly emanates from compressor 701 can be especially sensitive to anyshaking. Such movement can result in metal fatigue failure thereofcausing loss of refrigerant and subsequent failure of the refrigerationsystem. Those of skill will understand that a variation on the abovestrategy could be used where, for example, there could be a singlepredetermined time period that occurs and that is timed to exist for apredetermined period of time commencing before compressor shut-down andterminating substantially at the same time as power is shut-off thereto.

[0079] It will be clear to those of skill that the refrigeration systemdepicted in FIG. 31 can be adapted for use in an FCB machine asgenerally shown and described herein with respect to FIGS. 1-30. Inparticular compressor 701, high pressure line 702, condenser 704,refrigerant line 706, expansion valve 708, evaporator 710, hot gas valve716 and bypass line 718 could be substituted for compressor 270, highpressure line 271 b, and in particular discharge line portion 271 b′,condenser 273, refrigerant line 276 a, pulse valve 276, evaporator 274,hot gas valve 278 and bypass line 278 a, respectively and seen, forexample, in FIG. 18. Control 712 could likewise consist of thedistributed electronic control seen in FIG. 20 controlling compressor270 and motors 217. Thus, the determination that a predeterminedviscosity level had been reached or gone below would signal the shuttingoff or on, respectively, of compressor 270. Thus, hot gas valve 278could be opened in a manner to reduce any unwanted pressure differentialthat exists at shut down of compressor 270 as per the method shown inFIG. 32 or that exists at start up as per the above described procedurethat is analogous to that seen in FIG. 32.

[0080] Although some warm gas is directed into the evaporator as aresult of the method of FIG. 32, it was found that the amount requiredto obtain the advantages of that method of the invention herein does notunduly heat the evaporator. In an FCB machine as shown and describedherein wherein compressor 270 is sized at approximately 3 horsepower andwhere five pounds of 404 a refrigerant is used, the first predeterminedtime period can be approximately 1.5 seconds in duration and the secondpredetermined time period can be of approximately 1.0 second induration. It can be understood that bypass line 718 and hot gas valve716 generally comprise a mechanism that permits equilibration ofpressures between the high and low pressure sides of a refrigerationcompressor. Thus, bypass line 718 can extend directly between the highand low sides of the compressor bypassing the evaporator 710, asindicated by the dashed line 718 a.

1. A refrigeration system comprising: a compressor fluidly connected toa high pressure line extending between a high pressure outlet side ofthe compressor and a condenser, the condenser in fluid communicationwith an expansion valve for regulating a flow of condensed and cooledrefrigerant to an evaporator and the evaporator fluidly connect to a lowpressure inlet side of the compressor, and a bypass line having a hotgas valve therein for directing refrigerant from the high pressureoutlet side of the compressor to the inlet side of the compressor, and acontrol mechanism for operating the expansion valve, the compressor andthe hot gas valve for closing the expansion valve and at substantiallythe same time opening the hot gas valve for a first predetermined periodof time prior to a desired shut off of the compressor.
 2. The system asdefined in claim 1 and the first predetermined period of time elapsingsubstantially at the time of shut off of the compressor whereupon thehot gas valve is closed.
 3. The system as defined in claim 1 and thefirst predetermined period of time elapsing after the turn off of thecompressor whereupon the hot gas valve is closed.
 4. A refrigerationsystem comprising: a compressor fluidly connected to a high pressureline extending between a high pressure outlet side of the compressor anda condenser, the condenser in fluid communication with an expansionvalve for regulating a flow of condensed and cooled refrigerant to anevaporator and the evaporator fluidly connect to a low pressure inletside of the compressor, and a bypass line having a hot gas valve thereinfor directing refrigerant from the high pressure outlet side of thecompressor to the inlet side of the compressor, and a control mechanismfor operating the expansion valve, the compressor and the hot gas valvefor closing the expansion valve and at substantially the same timeopening the hot gas valve for a first predetermined period of time priorto a desired shut off of the compressor and the control closing the hotgas valve after the lapse of a second predetermined period of timefollowing the shut off of the compressor.